Researchers compared milvexian with enoxaparin for the prevention of blood clots in 1,242 patients from 18 countries undergoing knee replacement surgery who were enrolled between June 2019 and February 2021. They found that at a total daily dose of 100 mg or more, milvexian resulted in better clot protection but no increase in bleeding compared with enoxaparin, the control drug. Milvexian was evaluated in daily doses ranging from 25 to 400 mg; there was no increase in bleeding over this wide range of doses. Milvexian is unique in that it works by targeting factor XIa, a clotting enzyme that causes dangerous thrombosis, blood clots, but is not vital for stopping bleeding from injuries.